DeWitt Payne has done an interesting post here regressing ice core CO2 and deuterium temperature proxy information to examine the plausibility of CO2 amplification of temperature swings between ice ages. This is a favorite point of climate naturalists 🙂 regarding temperature swings in distant history, however there may be an explanation. Read on with an open mind, because physics doesn’t care what we think. -Jeff Id
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On The Relationship of CO2 and Deuterium Isotope Shift in the Dome C Ice Core
An understanding of the fundamentals of the standard hypothesis of what is called the atmospheric greenhouse effect is required to be able to concentrate on the true uncertainties. Proponents of a high climate sensitivity to doubling of atmospheric CO2 concentration claim that a high sensitivity is required to explain the magnitude of the temperature change from glacial to interglacial conditions. The shift in climate is thought to be triggered by small changes in insolation at high latitudes caused by cyclic changes in the Earth’s orbital parameters (Milankovitch cycles).
However, the size of the change in insolation is not sufficient according to the standard hypothesis to cause a temperature shift of the size observed. I have a problem with the assumption in the link above that interglacial climate conditions are stable and a decrease in insolation is required to trigger an ice age, but that’s not what I want to discuss here. Some mechanism or combination of mechanisms is required to amplify temperature change. The two main contributors are thought to be ice/albedo feedback and CO2.
We know with reasonable confidence from measurements of atmospheric samples trapped in bubbles in ice cores that CO2 is correlated with temperature as determined by the shift in deuterium/hydrogen isotope ratio. We also know with reasonable confidence from atmospheric radiation transfer theory and the characteristics of the infra-red absorption spectrum of CO2 that atmospheric CO2 acts to increase the surface temperature of the planet compared to a planet with no atmosphere.
However, the ice core measurements have CO2 concentration changes lagging temperature. Is amplification of temperature change by CO2 still plausible? Arguments against significant climate sensitivity for CO2 as demonstrated by ice core data include:
1. The change in CO2 concentration is an effect of temperature with a significant time lag so it can’t affect the temperature.
2. If CO2 really does amplify the temperature increase, the onset of the amplification should be obvious when temperature and CO2 are plotted on the same graph.
I will demonstrate that amplification of temperature change by CO2 is indeed plausible even though changes in CO2 concentration follow temperature rather than lead.
CO2 as a function of deltaD
Dome C deuterium isotope shift data1 can be found at the NOAA Paleoclimatology Program web site: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc_dd.txt
Dome C CO2 concentration data2 can be found on the same web site:
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/domec_CO2.txt
I’m not going to try to convert deltaD to temperature because it doesn’t represent a global temperature. I do assume that deltaD is proportional to global temperature. I also assume that equilibrium CO2 concentration is a linear function of deltaD, but the actual concentration lags behind the equilibrium concentration with a time constant of tau. CO2 concentration at time t will be a function of the CO2 concentration at time t will be a function of the CO2 concentration at t-1 plus the difference between the calculated equilibrium CO2 concentration (CO2e) at time t and the CO2 concentration at t-1 multiplied by a time lag factor: (1-exp(-(delta t)/tau).
Equation 1
CO2(t)=CO2(t-1)+(CO2e(t)-CO2(t-1))*(1-exp(-(delta t)/tau)
Where
Equation 2
CO2e(t) = m*deltaD(t)+k
The CO2 data and the deltaD data are not simultaneous. A deltaD data set that matched the times of the CO2 data set was created by linear interpolation between the values with dates that bracketed the CO2 dates. Then the Excel Solver function was used to minimize the sum of the squares of the differences between the calculated CO2 concentration and the measured concentration by varying m, k and tau. The result was:
m = 1.98225
k = 1062.88
tau = 2496.272
A regression of CO2 calculated vs. CO2 measured had an R squared of 0.98, an F statistic of 4037 and a slope and intercept that were not significantly different from 1 and 0 respectively. Using all the deltaD data from 30,000 years BP gave a concentration of CO2 at 70 years BP of 276 ppmv.
Contribution to the change of deltaD with time from CO2
Jeff Severinghaus, professor of geosciences at Scripps Institution of Oceanography, succinctly explains:
The contribution of CO2 to the glacial-interglacial coolings and warmings amounts to about one-third of the full amplitude, about one-half if you include methane and nitrous oxide.
The change in deltaD over the time scale of the Dome C CO2 data is 45.4 ppm. Assume that 30% of that change is due to CO2. Also assume that the change in deltaD is proportional to the logarithm of the ratio of the concentration of CO2 at time t to the initial CO2 concentration:
Equation 3
deltaD(t)= a*ln((CO2(t)/CO2(initial))
Thirty percent of the change in deltaD is 13.62 ppm. Initial CO2 concentration is 184.4 ppmv and the final concentration is 265.2 ppmv. Solving equation 3 for a gives a=37.5. Subtracting the change due to CO2 from the measured deltaD gives:
The basic form of the corrected deltaD curve is still about the same. The dip from the Antarctic Cold Reversal, that is about 1000 years earlier than the similar dip in Northern Hemisphere temperatures known as Younger Dryas, is somewhat enhanced. Acceleration of warming is only obvious because both results are plotted on the same graph.
Modeling CO2 as effect and amplifier
The measured data is noisy and the Antarctic Cold Reversal dip is an additional complication. Starting with a sigmoid forcing with no CO2 feedback similar in magnitude to that observed in the Dome C core with time steps of 100 years and the constants adjusted to give a curve with similar characteristics to the corrected deltaD curve above:
Equation 4
deltaD(t)=31.8/(1+exp((t-17000)/1000)-441.7
Then use Equation 1 to calculate CO2 concentration from the synthetic deltaD data gives:
Then use equation 3 to calculate the increase in deltaD from the calculated CO2 concentration and add that to the initial deltaD to produce deltaD fb1. Use the deltaD fb1 to calculate CO2 again and continue the process until the difference between iterations is no longer significant. I stopped after five iterations when the difference in the final CO2 concentration was less than 0.1 ppmv.
There is a subtle difference in shape and position of the deltaD with feedback curve compared to the no feedback curve, but it’s not at all obvious even with noise free data. If I fit a sigmoid curve to the deltaD with feed back curve I get this:
The fitted equation is:
Equation 5
deltaD(t)=46.27/(1+exp((t-16450)/1292.55)-442
Compare the constants in this equation to those in Equation 4.
Conclusion
There is no problem with the math for CO2 being both an effect and amplifier of temperature. There is also no problem with amplification when there is a time lag between the increase in temperature and increase in CO2. Given the time it takes to transfer heat to the deep ocean, which contains the bulk of dissolved CO2, a time constant of 2500 years is not at all unreasonable. A long time constant for oceanic CO2 evolution also supports the hypothesis that the recent increase in CO2 is from the burning of fossil carbon as the increase in temperature in the last 100 years would have had little effect on atmospheric CO2.
On the other hand, this is a double edged sword. While you can’t prove that CO2 didn’t amplify warming unless you know the precise shape of the underlying forcing, you also can’t prove that it did amplify warming or determine the magnitude of the effect and hence the climate sensitivity to doubling CO2 concentration for exactly the same reason. There are other known and possible feedbacks. Ice/albedo is probably the largest known. However, it is much less well understood than the greenhouse effect as it varies strongly with the latitude of the ice edge, not to mention the varying albedo of different kinds of ice, whether it’s snow covered or not or the effect of dust deposits. In addition, the contributions from clouds and aerosols are uncertain. Then there are the don’t don’ts, the things we don’t know we don’t know. So I’m not at all impressed with the argument that the climate sensitivity to CO2 must be high because glacial-interglacial transitions can’t be modeled without high climate sensitivity for CO2.
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References
1. Jouzel,J., et al. 2004. EPICA Dome C Ice Cores Deuterium Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-038. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.)
2. Monnin et al. Science v.291 pp112-114
DeWitt has provided the spreadsheet of the calculations for us HERE.
ln(CO2(t)/CO2(initial)), deltaD measured, deltaD calculated
the Air Vent 
Some data I picked up surfing the internet:
“Glaciation
For a number of reasons, the volume of glacial ice near the poles
waxes and
wanes over time. As a result, water is alternately taken from or added
to the
world oceans. This can result in sea-level oscillations of up to 200
meters. For
example, modern continental glaciers are 1.5 to 2.5 km thick and have
a total
estimated volume of 33 million km3. If we assume the maximum volume
of
Pleistocene glaciers to have been 71.3 million km3, Flint, 1971 then
the
difference is 38 million km3. Using the assumption that glacial water
volume is
91.7% of the volume of sea water from which it is derived, a sea-level
drop of
106 m can be accounted for by Pleistocene glaciation. Melting of the
present
Greenland and Antarctic glaciers would produce a sea-level rise of
approximately
60 meters.
The specific latent heat of fusion of ice at 0 ºC, for example, is 334
kJ.kg-1.
This means that to convert 1 kg of ice at 0 ºC to 1 kg of water at 0
ºC, 334 kJ
of heat must be absorbed by the ice. Conversely, when 1 kg of water at
0 ºC
freezes to give 1 kg of ice at 0 ºC, 334 kJ of heat will be released
to the
surroundings. (Note for educators).
The total mean mass of the atmosphere is 5.148*10^18 kg
A 4C rise or higher this century would see the world warm almost as
much in 100 years as it did during the 15,000 years since the end of
the last ice age.”
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Putting it all together, 71.3 million k3 ice *0.917 vol ice/vol
water=
65.3821 million cubic kilometers of water.
1 cubic meter= 1000 kg.
1 cubic km = 10^12 kg
65.3821 million cubic km= 65.3821*10^18 kg
Total heat to melt glaciers =65.3821 *10^18 *1000*334 kj=2.18*10^25
joules.
Cp air= 1.012 joules/gram K =
1012 Joules/kg K * 5.148^10^18 =5.209776 *10^21 joules
4C increase=2.0839 *10^22 joules
So about 1000 times as much heat went into melting the glaciers at
the end of the Pleistocene as went into heating the atmosphere,
implying CO2 had only a negligible effect- assuming the glaciers melted before temperatures started going up. – A. McIntire
DeWitt
“Proponents of a high climate sensitivity to doubling of atmospheric CO2 concentration claim that a high sensitivity is required to explain the magnitude of the temperature change from glacial to interglacial conditions.”
It needs to do more than just that, it needs to warm the Earth to the temperatures experienced in the Cretaceous and other ‘hot house’ climates. This requires a high CO2 sensitivity as solar irradiance in those hot house climates was significantly lower than in recent times.
Alan
“Melting of the present Greenland and Antarctic glaciers would produce a sea-level rise of
approximately 60 meters.”
Earlier climates that featured no polar ice caps (i.e. most of the Earths history) typically had sea levels around 300m higher than present.
DeWitt, could changes in thermaholine circulation due to freshwater flux variability contribute to amplification?
“It needs to do more than just that, it needs to warm the Earth to the temperatures experienced in the Cretaceous and other ‘hot house’ climates. This requires a high CO2 sensitivity as solar irradiance in those hot house climates was significantly lower than in recent times.”
This claim is far too strong, and belies a disturbing degree of certitude as to the nature of these paleoclimate changes and there causes. True enough the classical solution to the faint young sun paradox is to use CO2 and positive feedback…that doesn’t make said solution correct (far from it) and there could be any number of explanations. I understand Lindzen is working on a paper which shows how thin cirrus in the tropics could resolve the issue. I’ve heard other ideas thrown around. And I see no reason why your logic couldn’t be extend to a situation where CO2 doesn’t change at all, but temperature does-clearly sensitivity is infinite! Sure, physically absurd, but necessary to expose the fallacy.
The sun was about 70% as luminous as it is now 4.6 billion years ago. Assuming a roughly linear increase in luminosity, the sun would have had a luminosity of 4.45/4.6 = 0.967 at the start of the Cretaceous. Since luminosity increases as the 4th power of temperature, everything else being equal, the temperature of the earth would have been (0.967)^0.25 = 0.992 of present temperatures: not that much different than now. Slight differences in surface albedo could more than make up the difference. The distribution of land and sea would have been different enough to easily make up the difference in albedo changes: For one thing, Antarctica is now covered in ice- during the Cretaceous it wasn’t.
A. Mcintyre
Yes, Antarctica wasn’t covered in snow, however it’s latitude was roughly the same. The world was a lot hotter in the Cretaceous, my point is that you need to get the world that hot. There had been very large ice ages prior – in the Permian and Neoproterozoic escpecially – how did the world warm up? You say that solar luminosity would make it 0.992 x current temps. But the Cretaceous was probably between 7 and 14 degrees warmer. De Witt in his essay above says that you need CO2 to explain the changes between the coldest parts of this ice age and interglacial periods. We also need CO2 as a greenhouse gas to exlpain the even higher temps during (for example) the Cretaceous.
Timetochoose
“that doesn’t make said solution correct (far from it) and there could be any number of explanations. ”
This is apoor argument. Why would you ignore a hypothesis that works for some unknown hypothesis? we KNOW temps were higher, we KNOW the sun didn’t cause the higher temps, we KNOW that CO2 was higher, we KNOW that CO2 is a greenhouse gas.
Here is a good paper. It shows that albedo changes alone cannot explain the temp increase in the Cretaceous.
Click to access Bice_Norris_2002.pdf
“However, climate model simulations that produce reasonably
good matches to MK temperature estimates indicate
global mean surface temperatures of 21–28C [Poulsen,
1999; this study]. To attain these temperatures without
greater greenhouse warming, an albedo decrease of 8–
17% would be required, considerably more than the 2–
4% reduction calculated for MK land/sea distribution, icefree
poles, and global green vegetation coverage [this
study]. If proxy estimates of Ts and A are realistic, a
greenhouse effect 4–12C greater than the modern is
supported for the MK.”
DeWitt, could changes in thermaholine circulation due to freshwater flux variability contribute to amplification?
“KNOW” “KNOW” “KNOW” Again, the arrogance with which you approach such a complex subject is striking. I’m not “ignoring a hypothesis which works” I’m questioning whether said hypothesis is really the only possible explanation. To my mind, the situation going that far back is next to unknowable.
Re: #7,
Re: #6,
Let’s see if I can remember to close the blockquote tag this time.
Need is a little strong. I’m saying that CO2 amplification is a plausible hypothesis and very likely made some contribution to the temperature change. The size of the amplification, however, cannot be determined from ice core evidence alone because there are too many other things we know much less about starting with ice/albedo feedback.
The current view of the ice/albedo feedback mechanism is that if the ice edge gets too close to the equator (closer than 50 degrees according to Budyko), you get runaway cooling and an ice ball planet. There is some evidence that this may have happened once, but it’s controversial. It seems likely then that there is some unknown bounding mechanism for ice/albedo feedback on the low temperature side. Budyko, btw, did not believe that Milankovitch cycles explain glacial interglacial shifts. He preferred volcanoes.
The subject of the high temperature at the poles during periods like the Eocene Optimum is even more complex. The real question, IMO, is not how did it get so warm, but why did it start to cool? Then there’s the Paleocene/Eocene Thermal Maximum. That’s probably the best paleological evidence for ghg forcing of climate change. Those are subjects for future essays, though.
DeWitt,
It appears that the temperature has only varied a relatively small amount (12C to 22C) while CO2 has varied from 200 ppm to 7,000 ppm over the last 600 MY, with a relatively low correlation between them. The present average temperature is slightly below the mid point on that range (about 16C). The locations of the land masses (which have moved a lot in the multimillion year time scale)and the altitudes of mountains strongly affect ocean current and atmospheric circulation. Water temperature and biological activity strongly affects CO2 levels. By time you add tilt of the Earth, Solar direct and indirect variation, volcanoes and other causes, and the changing Albedo from ice distribution and clouds, the cause of the relation between temperature and CO2 levels in the more distant past can not be simply deduced.
The ice core records over the last several hundred thousand years show a variation of the CO2 from about 200 ppm to about 300 ppm (except for the near present), but the smoothing effect from the long time to seal the ice to a solid loses or greatly reduces any short term larger variation (on the order of 100’s of years). We thus have very limited detail of what the exact CO2 vs temperature relationship is except over the recent time period of about the last 50 years, where reliable direct measurements were made.
Direct effects of increasing CO2 and Methane on heat trapping are well understood, and it is known that in the absence of feedback from WATER VAPOR, that the doubling of effective CO2 (including Methane effects) would raise the average temperature about 1.2C. The whole argument hinges around the WATER VAPOR feedback. The models that claim a positive feedback averages in a 2.5X gain to a net rise of at least 3C. The negative feedback argument (Roy Spencer and Linzen)seems to say the actual increase will be less than 1.2C. The question is who is correct.
The only data we have from ice cores and ocean sediment cores (which may be the only reliable proxy data more than a few hundred years old) seem to indicate that the Northern hemisphere has gone through warming and cooling cycles of up to 2C up and down about every 1,000 years or so, and that the present temperature is a recovery from a low period called the little ice age. The present temperature in fact seems to be about average (not unusually high) for the Holocene, and is clearly lower than several periods even in the last 3,000 years. The present trend is not continuing upwards, but down, although this trend is too short to make an issue.
Given that variations in CO2 are not responsible for the previous temperature variations over the last 3,000 years, and that the present rise rate and level are NOT unusual, the argument for positive feedback falls flat on its face. The claims of global dimming and natural variability are possibly the cause of the disagreement, but seem an unrealistic stretch.
The scientific method does not require that every possible claim of a hypothesis has to be falsified, only that at least one critical claim is falsified. The AGW models have been falsified in general. The specific claim of positive feedback has no falsifiable claim that can be tested, that is only valid if the hypothesis is correct. I see no possible reason for a 3C or 4C rise this century or even 2 or 3 centuries, but I do see a possibility of the ending of the Holocene in the not too distant future.
The original post had a mistake in equation 1 that has now been fixed. The original equation was:
CO2(t)=CO2(t-1)+(CO2e(t)-CO2e(t-1))*(1-exp((delta t)/tau)
The difference term is now (CO2e(t)-CO2(t-1)). I wrote the post from my notes and failed to check against the equation I actually used in the spreadsheet after the equation in the notes didn’t work correctly.
Re: #11,
A modified version of the Ruddiman hypothesis that the only reason we are not well on our way back to glaciation already is that humans have sufficiently altered the climate by a combination of land use/land cover changes (agriculture, e.g.) and greenhouse gas emissions (methane from rice culture and fossil fuel burning) is not implausible. Expanding on my comment in the original post on Milankovitch cycles, I don’t think a trigger is necessary to cause a return to glacial conditions. Glacial conditions are currently the norm and the interglacial periods are a transient response to some impulse forcing.
Re: #1,
I’ve also played around with ice sheet calculations. The energy involved is indeed huge, but you have to consider the time factor as well. Spread the heat out over hundreds of thousands or millions of years and the net forcing required in W/m2 over the surface area of the planet becomes quite small. For example, to freeze enough water to drop the sea level by 120 meters over 100,000 years requires a net forcing of only -0.08 W/m2. That’s a worst case figure assuming the heat of condensation of the water has to be lost as well, which adds an additional almost order of magnitude to the energy change.
While I have not yet read in sufficient detail to comment on DeWitt’s calculations, I have always liked his thoughtful approach to the examining what we can accept with good confidence in theories related to AGW and where we require more evidence to tighten the uncertainties associated with some of these theories.
That approach seems in sharp contrast with some of those on both (or the many) sides of the AGW issue that seem not accepting of anything from the other side.
DeWitt,
Thanks for the post. I have some basic questions about whether ice core proxies work physically as they are claimed but they relate only to some sort of engineering verification of their function. It might be interesting to have a discussion about the verification level of proxies in this case.
Reading the above post, am I understanding that the main conclusion is that CO2 temperature amplification factor of about 30% is not invalidated by the lag in ice core proxies? I ask because there are some broad statements about solar output and gas forcing in the commentary.
I’ve studied a very few specific items in climatology so far and a great deal of the discussion in the thread is new information to me.
Roy Spencer has a related post at his website: http://www.drroyspencer.com/
He says that the degree of climate sensitivity needed to explain 100,000 BP temps is difficult to reconcile with current observations, and suggests that an unknown forcing mechanism (and lower climate sensitivity) might explain the Vostok data.
Any comments DeWitt?
Layman-Spencer seems to be assuming that the Vostok temperature changes match one to one with global changes-that’s highly unlikely, the global change was probably 1/4th the change near the poles.
Laymen, The section of the CO2 graph DeWitt used isn’t enough of a record for my liking. He is limited here in what can be resolved.
In Dr. Spencer’s graph.
The falling CO2 concentrations lag by a lot more than the rises. The rises are almost perfectly on top of the temp proxy. In the 120K year range the drop in temp precedes CO2 by a long long time yet temps due to ocean damping should react the same both up and down. I’m guessing there’s more to it than I’m seeing. Perhaps DeWitt or some of the others have an answer but when CO2 remains that high and temp drops that low it doesn’t look like only CO2 feedback to me. (just thinking out loud, I don’t have the background) Maybe increased biology holds the CO2 concentration up after a warm time.
#18
I think you raise a good point here. Is this matter discussed in the literature anywhere?
Actually, I this quote shows that Spencer is aware of what the Vostok data represents:
“A second problem has been that the positive correlation with Vostok (at the South Pole) came from NORTHERN Hemispheric forcing, not from the Southern Hemisphere. In the south, the Milankovitch forcings were out of phase with the temperature response in the Vostok ice core record. This has presented the problem of how Northern Hemispheric changes in solar forcing could cause such huge changes in Antarctic climate.”
Layman-the fact that poleward temperature changes tend to be much greater than global means has been known for some time (at least since Budyko and Izreal, two Russians back in the 70’s)
I’m not saying that it totally invalidates the possibility that Vostok shows a low sensitivity, but the claim:
“If CO2 is the main forcing in the Vostok record, then it takes only about 10 ppm increase in CO2 to cause 1 degree C temperature change.” would only be true of the Antarctic. I can’t think of the specific reference, but the Budyko-Izreal distribution points to something on the order of 4-3 times the global mean at the poles. See slide 14 here:
Click to access Lindzen2_maj_06.pdf
#22
Yes I see your point on Spencer’s claim. DeWitt, are we missing something here?
On poleward heat re-distribution, I think I am going to try to do a little reading to try to understand the relationship and uncertainties of global temps vs. Antarctic temp proxy data. If anyone knows of any references – much appreciated.
Re: #16,
Yes. It looks to me like a wide range of amplification factor is plausible. Higher amplification is going to distort the underlying forcing more, but since we don’t know the shape of the forcing anyway, how can we tell?
Re: #18
The confounding of ice core temperature with global temperature by Spencer jumped out at me too. That’s why I used deltaD rather than delta TS. I came across a reference on polar amplification that included a very wide range of values but didn’t save it. Reading between the lines of this paper, it looks like they see a cooling of tropical SST of about 3 degrees at the LGM compared to a 9 degree change in temperature of the Vostok core. I don’t agree with their conclusion on climate sensitivity because they assume that 100% of the tropical temperature change is caused by ghg changes.
Re: #20,
If you google various combinations of polar, temperature, tropical and change, you should find lots of references, although most of them will probably be model calculations.
Using worldwide data averages as a function of time may miss an important fact. Regional large temperature shifts up and down may not (and probably do not) all occur at the same time, so an integrated average may look small but consist of larger pieces not lined up at the same time. For example, I noticed that the Sargosso sea, Greenland, and Antarctic temperature variations all occurred about as fast and with about as large amplitude. However, the peaks and dips of the three regions did not exactly line up. If my conjecture is correct, the claims that the poles heat (and cool) faster than the rest of the world may be false. It may only imply that a selected but limited size region is more correlated in change than the sum of regions over the entire Earth. I recently saw a blog (I can’t remember where) that stated that Europe and Northern US both had unusual large temperature swings for several years, but at slightly different times. This also tends to support the idea. If the swings at the poles lose their unique speed of change feature, this falsifies another common assumption.
Not quite tropical, but in the southeast pacific, you already get down to about 6 degrees from LGM to present:
http://junkscience.com/MSU_Temps/Kaiser2005.html
That’s “midlatitude” so it looks like the tropical would probably be smaller still.
lweinstein-in the short term (for instance, with AGW) amplification at the poles is indeed apparently subordinate to some mode of variability or another:
http://climatesci.org/2009/06/01/new-paper-arctic-air-temperature-change-amplification-by-chylek-et-al-2009/
However, on the geological timescale, it is much more established.
Timetochooseagain
““KNOW” “KNOW” “KNOW” Again, the arrogance with which you approach such a complex subject is striking. I’m not “ignoring a hypothesis which works” I’m questioning whether said hypothesis is really the only possible explanation.”
Arrogance? That’s your best argument? What’s arrogance got to do with it?
“To my mind, the situation going that far back is next to unknowable.”
Probably because you haven’t actully read any papers on paleoclimate. The fact that the present climate is one of the coolest in the Earth’s history is pretty clear. That we need a greenhouse effect to explain these climates is clear.
Did you read the paper I linked?
Re: #28 Nathan,
I read the paper and there are a lot of caveats both stated and implied. For example, warm polar regions are going to have a substantial lapse rate feedback (the atmosphere will be less dense leading to higher altitude and lower temperature at the point where the optical density at the center of the CO2 band drops below 1.0 resulting in higher forcing) compared to the current cold polar regions. Does the model used properly account for that? Who knows? What I gathered from the paper was that the model appeared to be used as a black box that pumped out numbers when the appropriate knobs were tweaked. The authors also mentioned the uncertainty in high level polar cloud contribution and heat transport. I’m not saying that high levels of CO2 did not contribute to MK warming, but what was the climate sensitivity to CO2 then and is the sensitivity under the warm MK conditions the same as now or different? Again, who knows? When you play with the Archer MODTRAN calculator, the climate sensitivity increases as the CO2 concentration increases and that implementation of MODTRAN has no facility for changes in atmospheric density with temperature that might accelerate that effect.
Wow, you scold me for calling you arrogant, continue to pontificate, and then accuse me of ignorance. Don’t be a jackass. I have read the paper, I’m not impressed, it doesn’t make anything “clear”. Deal. Pisser.
Dewitt
So because you don’t know the answers to these questions, there is doubt? Well can’t fault your logic.
“I’m not saying that high levels of CO2 did not contribute to MK warming, but what was the climate sensitivity to CO2 then and is the sensitivity under the warm MK conditions the same as now or different? Again, who knows?”
So will you attempt to solve this conundrum? Or will you throw your hands high and say “who knows?”. This is not a contribution, it’s a statement of personal skepticism, which is largely useless. Why does it matter that you don’t accept their results? Apparently the authors of the paper were satisfied enough to write it. Their work is not alone either. The amount of literature on paleoclimatology is enormous, CO2 (or more specifically a greenhouse effect) is required to explain the changes in climate over the Earth’s history.
The problem I have with your whole argument is this:
“So I’m not at all impressed with the argument that the climate sensitivity to CO2 must be high because glacial-interglacial transitions can’t be modeled without high climate sensitivity for CO2.”
Because that is not the whole argument. You have not considered the case for high CO2 sensitivity based on more ancient climates. Your personal skepticism is irrelevant unless you can come up with a better solution. You need to provide an explanation for the previous climates. If you can’t, then a high CO2 sensitivity will win.
I’ve done my freakin’ research, I’m no dumb hick hack, and “Nathan” treats me like shit and he doesn’t even know me. WTF? I know what I’m talking about. The paleo stuff he is pushing as “proof” is nothing of the kind. I raise objections, he repeats assertions, and then proceeds to personal attacks. There is where I draw the line. If this is the level of engagement I get from him I want none of it. Whatever. I’m done. Let Dewitt or someone else with more patience deal with your “arguments”. I won’t be disrespected. My fuse is to short. I’m ghost.
[snip]
[snip]
[snip]
I got the same estimate of CO2 amplifies the warming by roughly 50% as DeWitt Payne did, but
my calculation was a crude, algebraic “order of magnitude” estimate based on the relative periods of
temperature rise vs temperature fall. My post was on the December 11, 2008 “DESMOG BLOG”
http://scienceblogs.com/deltoid/2008/12/650_international_scientists_e.php
“Notice on the Vostok icecore data graph that when the temperature goes up, CO2 follows quite rapidly. When the temperature drops drastically, CO2 remains high and only drops gradually, so obviously CO2 is a lagging indicator, and has only a secondary effect, less than the immediate forcing of the sun.
http://home.scarlet.be/~ping5859/co2tempice.html
The realclimate doubletalk drive explanation doesn’t address the followup COOLING trend.
Obviously the feedback effect of CO2 must be less than the primary effect of the sun.
For a simple linear model, if the effect of the sun on climate is F1, and the effect of CO2 is F2, and the combined forcing is F1 + F2, the the F2 feedback effect of CO2 MUST be less than the forcing of the sun alone. In other words, F1 + F2 < 2 F1.
If not, when the sun switches to a cooling phase and CO2 is still high, you'd get – F1 + F2 is greater than zero, and you'd never have a followup cooling trend.
The difference in period of warming and period of cooling will give you an idea of the relative feedback of CO2. If the cooling period is 3 times as long as the warming period, you get a rough estimate of the effect of CO2 compared to solar by solving the simple algebraic set of equations F1 + F2 = 3 F1 – F2 = 1
To get F2 is 1/2 F1. So if the expected warming by the sun is 1 C, the additional effect of the CO2 feedback would be 0.5 C. "
I didn't treat my calculation seriously, I thought of it as a "Maximum Possible Effect" of CO2.
Rise to the occassion TTCA.
“You totally fail to understand my point”
ok, you said
“To my mind, the situation going that far back is next to unknowable.”
You seem to be dismissing the science of geology here. A lot of information and knowledge of the past is known. Even way back to the Archean.
Can you express that statement in a more precise or alternative way?
MY BALL MY HOUSE. Play nice.
It’s a friggin’ CO2 lag, nobody lost a football game.
Yes. I’m not denying geology. Quit acting like you are fighting someone stupider than you. It’s offensive. Let’s be clear, by “unknownable” I mean that the perfectly legitimate geological data do not as you bizarrely categorically assert over and over, admit only one possible combination. Yes it was warmer back then. No, we don’t “know” why. We have hypotheses, and no shortage of them either. To pretend like only the one hypothesis is valid or compatible with the data is ridiculous.
And I mean seriously, denying geology? Did you even pay attention to half the stuff I said in this thread? I cited a lot of paleo stuff. Get off your high horse. Quit this god complex nonsense. Or don’t, I really don’t care.
Geo thermal heat…
night nite
Alan
As the world (or more specifically the oceans) starts to cool due to changes in the Earth’s orbit (Mlkankovitch cycles) the solubilty of CO2 increases. The reason it takes longer to cool down that warm-up is that you still have relatively high CO2 (compared to the bottom of an ice age), it shows that CO2 is always a +ve forcing.
TTCA
“Yes it was warmer back then. No, we don’t “know” why. We have hypotheses, and no shortage of them either. To pretend like only the one hypothesis is valid or compatible with the data is ridiculous.”
The CO2 hypothesis works fine. This whole “we don’t know” or “we won’t ever know” concept is redundant and is essentially the basis of post-modernism. It is meaningless, what needs to be considered is what we do know, and we do know a lot about paleoclimates.
I was challenging DeWitts idea that
“I’m not at all impressed with the argument that the climate sensitivity to CO2 must be high because glacial-interglacial transitions can’t be modeled without high climate sensitivity for CO2.”
Because it’s based on more than the glacial-interglacial transitions.
#39 Jeff Id
…or a hockey game. 😉
Nathan,
.
That’s a logical fallacy, the argument from ignorance. If I can’t come up with a better solution, then the proposition must be true. Incorrect. I don’t have to come up with a better solution to consider the paper’s conclusions questionable or invalid. All I have to do is raise a reasonable doubt. I don’t have to convince you either, it’s the other way around and so far you’re not doing very well.
Dewitt
You didn’t show anything wrong with the paper, you said you didn’t know if it was wrong. Which is like me saying “I don’t know if you’re wrong…” ie pointless.
You have also taken me out of context. That comment wasn’t in relation to that paper. Here is the whole quote:
“The problem I have with your whole argument is this:
“So I’m not at all impressed with the argument that the climate sensitivity to CO2 must be high because glacial-interglacial transitions can’t be modeled without high climate sensitivity for CO2.”
Because that is not the whole argument. You have not considered the case for high CO2 sensitivity based on more ancient climates. Your personal skepticism is irrelevant unless you can come up with a better solution. You need to provide an explanation for the previous climates. If you can’t, then a high CO2 sensitivity will win.”
I am trying to convince you that your question (in it’s present form) is currently poorly framed, as the sensitivity evidence comes from more than just the glacial-interglacial cycles.
Saying, “I don’t know if you’re wrong” is not pointless. It’s a way of starting to think about something. The thing that’s bad is when skeptics (either blog authors or hoi polloi hangers-on) think that “I don’t know if you’re wrong” is more than what it is.
Perfect example:
I don’t KNOW if Lucia is wrong with her latest 8 year trend, where she claims at 95% confidence that the trend is different than a predicted rise. For one thing, I don’t know how she did her calcs exactly. But I do know what I would check to look at her work:
A. If the IPCC 2deg/C was supposed to be same rate throughout the century (i.e. not shallower currently).
B. If AR(1) is appropriate, in particular for MONTHLY data. (As you divide a series with memory to shorter time frames, obviously the point to point autocorrelation becomes larger.
C. If she looked at ALL of the sattelite data (not just last 8 years) to give her, her memory structure and term.
D. If she is using the Lund approximation properly. (An expert I talked to had similar concerns as above, and he is familiar with the Lund note and its assumptions.)
C.
I never said “we wont ever know”…although that raises the question of why “post modernism” is an insult…I suppose it could be one, but I don’t understand why. Whatever.
“You need to provide an explanation for the previous climates. If you can’t, then a high CO2 sensitivity will win.”
Um….No. Speaking of postmodernism…That’s exactly like the argument for the Hockey Stick that is used against M&M. Demand they offer an “alternative” reconstruction or….the Hockey Stick “wins”. Never mind the problems with your hypothesis. One must offer an “alternative” or shut up.
“You need to provide an explanation for the previous climates. If you can’t, then a high CO2 sensitivity will win.”
I don’t understand how we come to a point where if we don’t have an answer now it must be another possible answer. If nothing is proven, nothing is proven. Don’t know is also an answer – and IMHO probably the correct one.
What’s been shown here is that a stretch of the Dome CO2 record can be closely replicated by empirical curve fitting via the proxy temperature record. That’s pretty easy, given that temperarature consistently leads. To show that CO2 has any physical impact on temperature the exact opposite construction would be necessary, without relying on future values of either variable. That’s the hard part.
Jeff
Because the high sensitivity for CO2 explains the Earth’s climate history very well – it is an answer that presently works. I was saying that DeWitt’s claim that he wasn’t impressed by the need for high-CO2 sensitivity based on interglacial-glacial changes was poorly framed. I was suggesting he check the evidence based on ealier climates. I am not saying that there is no alternative, but we shouldn’t ignore that CO2 levels go a long way to explaining most of the climate in the Phanerozoic. In fact it is remarkable that it does.
TTCA
Everything I say you take as an insult. I don’t know why.
TCO
You can do everything ou said without saying “I don’t know if you’re wrong”. It’s a redundanct step.
Because either 1. I’m too thin skinned or 2. You’re patronizing. Or 3. Both.
I’ll go with 3. But that’s just me.
We shouldn’t “ignore” it, but we shouldn’t take it for granted either. I think there are problems with it (equator to pole temperature differences for one) but not necessarily fatal ones.
Looking at the radiative forcing with constant relative humidity using Archer Modtran:
Tropical atmosphere, constant RH, doubling CO2 from 375 to 750 requires a surface temperature increase of 1.5 C to rebalance outgoing LW radiation at 100km. 4000 ppm CO2 require an increase of 5.7 C, a climate sensitivity of 1.7 C/doubling. That’s 32.2 C surface temperature, btw. Going from 180 to 280 ppm only requires a change of 0.64 C. CO2, then, only explains a fraction of the change in temperature from glacial to interglacial, but is probably much more important going from an Eocene Optimum or Cretaceous climate conditions to current or pre-industrial conditions.
If the climate sensitivity were indeed 6 C/doubling, then 4000 ppm CO2 would result in a 20 C or more increase in temperature, depending on your assumptions, (6*ln(4000/375)/ln(2)= 20.5) or a global average of ~35 C. It would be more than 35 C if you assume that the current temperature is not the equilibrium temperature for 375 ppm CO2. So paleoclimate data actually puts an upper limit on climate sensitivity.
DeWitt I think this looks wrong:
“Tropical atmosphere, constant RH, doubling CO2 from 375 to 750 requires a surface temperature increase of 1.5 C to rebalance outgoing LW radiation at 100km. 4000 ppm CO2 require an increase of 5.7 C, a climate sensitivity of 1.7 C/doubling. That’s 32.2 C surface temperature, btw. ”
Do you mean 22.2 rather than 32.2? That’s right at the bottom end of the estimates for the temp for the middle Cretaceous. So the sensitivity of 1.7 per doubling is at the lower end for the Creataceous.
I doubt the 6C per doubling myself. I think that value is too high. Personally I think it would be between 2 and 3, but can’t back that up with any data.
When you heat ocean water, it becomes less dense (as long as you are not near freezing), so it tends to stay on the surface. When you cool water, it becomes more dense and tends to sink faster. This means the warming phase of glacial to interglacial periods happen relatively fast, since the warmer surface water allows more water vapor to form, and probably would result in more water vapor in the atmosphere, since the cold Earth likely has less clouds. The water vapor plus a modest increase in CO2 both boost the warming rate, but the water vapor probably is by far the biggest cause of the warming rate. The larger depth of mixing as you cool would tend to slow down the rate of surface cooling, and thus slow down the passage back to glacial. The presence of warmer or cooler surface water also probably would impact the rate of sea ice formation and melting, and both are affected with a similar asymmetry in warming and cooling.
Nathan.
The surface temperature for the Tropical atmosphere in MODTRAN is 299.7 K or 26.5 C, not the global average temperature of 15 C. So yes, adding 5.7 C increases that temperature to 32.2 C.
Leonard,
Ice/albedo is the amplifier of choice for me at a glacial maximum. Even a small increase in the length of summer should start to lower sea ice extent and decrease albedo. The edge of the sea ice, especially in the Southern Hemisphere, is always going to have a large seasonal fluctuation. Start the edge moving South and temperature should start going up. I’d like to see Milankovitch cycles calculated for insolation at 65 S rather than 65 N as is customary. I’d also like to see a Koutsoyiannis type (long term persistence, Hurst coefficients, etc.) analysis of glacial-interglacial cycles. A chaotic system can show what looks like regular cyclic behavior but isn’t.
DeWitt Payne: See page 9:
http://www.atypon-link.com/IAHS/doi/pdf/10.1623/hysj.54.2.394?cookieSet=1
TTCA,
After futzing around with the link (something about cookies, groan), I got through. That is indeed what I was looking for, thanks. Another nail in the coffin of climate stationarity.
DeWitt
According the paper I sent you the SST in the tropics in the Cretaceous was 35C, So that is supporting a value close to 6C. That is also assuming that CO2 levels were 4000ppm. The paper I linked shows that levels could range from 900ppm to 4000ppm. Again this supports a higher climate sensitivity.
Click to access 165pal~1.pdf
TTCA
That correspondence seems to support my notion that it is earlier climates that support a higher sensitivity.
It’s also from 1993… Do you have anything more recent?
Nathan,
Do you really think that current tropical SST’s are 15 C or anywhere close to that low? According to this map, current tropical SST’s are in the high twenties almost 30 C. So the 375 ppmv CO2 surface temperature in MODTRAN of 26.5 C is, if anything, low. That 35 C, btw, was the maximum estimated and the CO2 estimates in the article were all over the map (900 to 4500 ppmv). The way I read the article the authors took the easy way out and assumed they were all correct and that the difference was due to variation over time. In fact, there are so many stated caveats in the article you linked that it is less than definitive to put it mildly. For just one example from the conclusion section:
[my emphasis]
I particularly like the combination of ‘suggestive’ and ‘demand’.
DeWitt
Err no I don’t think tropical SST is that low. Nor did I say that.
Indeed the estimates of CO2 vary from 900 to 4500 ppm, but these numbers come from a variety of sources such as sizes of leaf stomata.
Why are you amused by that language?
If you look at the abstract is even clearer:
“we estimate upper ocean water temperatures from oxygen isotope measurements of well-preserved late Albian–Turonian planktonic foraminifera and compare these against temperatures predicted by general circulation model (GCM) experiments with CO2 concentrations of 500–7500 ppm.”
So the temps were determined from oxygen isotopes in the forams, then they used models to determine what CO2 levels give those temps.
Also note that independently of this they obtain CO2 levels from proxies;
“The upper bound to this range comes from fossil leaf stomatal index (SI) measurements of Cenomanian and Turonian Ginkgo specimens from Siberia that yield CO2 values of 4000–5500 ppm [Retallack, 2001]. At the bottom of the range, Freeman and Hayes [1992] provide estimates of 830–1100 ppm CO2 based on the carbon isotopic composition of marine organic compounds in Cenomanian and Turonian sediments of the Western Interior Seaway and North Atlantic.”
They also note that this period featured highly fluctuating values of CO2. There was huge amounts of volcanism in the Cretaceous – that’s the best way to really push up CO2 values.
Only if you buy Hoffert and Covey’s counter arguments. You are predisposed to, but from my perspective they are not so convincing.
And no, I don’t. However Lindzen clearly still holds the view he espoused there:
Click to access Lindzen2_maj_06.pdf
From what I can tell, H&C’s argument is the same as yours-namely that until Lindzen creates a fancy model like they did, he should shut up-essentially “Mine’s bigger than yours”.
TTCA
How can Lindzen back up his claims without a quantitative model? Is he suggesting that the modelling he does in his head is better than using a quantitative model?
At least these scientists have taken data, temp and CO2 proxies, then used existing models to check that it all holds together. The temp proxies, CO2 proxies and model runs essentially confirm each other.
Jeez, is it even worth pointing out where you are going wrong?
One doesn’t need a model to show that H&C’s argument (and similar subsequent ones) don’t rule out other possibilities. One only needs to describe a plausible alternative. The onus is on he who contends the alternative is wrong to eliminate it. Merely stating that there is more than one hypothesis that has not been eliminated does not require that one prove or disprove either. H&C, and others never eliminated the alternative possibility, they just falsely asserted that only one solution was possible until everyone who wasn’t paying enough attention bought it. God olnly knows why.
TTCA
So what is the alternative?
And you need to model the alternative, which is what H&C were asking Lindzen to do.
And your final claim is ridiculous.
“H&C, and others never eliminated the alternative possibility, they just falsely asserted that only one solution was possible until everyone who wasn’t paying enough attention bought it.”
They don’t need to eliminate alternatives, they just need to demonstrate that their solution works.
This is the big problem here. You seem to be saying that we need to consider alternatives. Science does, all the time, consider alternatives. However the CO2 greenhouse hypothesis is by far and away the best hypothesis. It works, and has been supported over and over.
“They don’t need to eliminate alternatives, they just need to demonstrate that their solution works.”
They do if they want to claim exclusivity.
“far and away the best hypothesis”
You have no evidence that it is the best, only the repeated assertion you make over and over that
“It works, and has been supported over and over.”
Classical physics worked and was supported over and over. But relativity and quantum mechanics refined classical physics and it is entirely fair to say that, while approximately correct, classical physics was “wrong”. Now I’m not claiming that either Hypothesis (either H&C’s or Lindzen’s is the refinement or the approximation, only that one needs to eliminate one possibility to be certain of the other.
Quit trying to shift the burden. Show that one and only one solution works, or admit that you can not claim that CO2 and high sensitivity is the only explanation. Otherwise your certainty is totally baseless.
Adios amigo.
TTCA
What is your alternative? You need an alternative…
“One only needs to describe a plausible alternative. The onus is on he who contends the alternative is wrong to eliminate it. ”
You forgot to describe your plausible alternative.
TTCA
Also I said it was the best hypothesis.
You are verballing me.
Here are some quotes of mine that show my position:
“we KNOW temps were higher, we KNOW the sun didn’t cause the higher temps, we KNOW that CO2 was higher, we KNOW that CO2 is a greenhouse gas. ”
All of these are knowns.
I have never said that we KNOW “CO2 and high sensitivity is the only explanation.”
What I said was “However the CO2 greenhouse hypothesis is by far and away the best hypothesis. It works, and has been supported over and over.”
I’m not the one offering an alternative. Why is Lindzen’s not plausible? Apart from the cavalier dismissal that he needs a “model” I see no real objection.
You offer no evidence for it working “the best” just the same assertion again. Show me a clear test which demonstrates it’s superiority to other alternatives. “Best” would appear to me a subtle suggestion that their is enough evidence to favor it over other possibilities (they can be, do a degree, eliminated) and yet you simply assert what you should be able to show. What gives?
BTW, the quote that shows your position unfortunately comes off with a tone quite different than one would expect from someone willing to admit their might be alternatives. Poor communication can only confuse…
TTCA
Without a model how can Lindzen test his hypothesis?
“Show me a clear test which demonstrates it’s superiority to other alternatives.”
Because when they built the model it fit the observed data. So the isotope data, gave them the temp. They worked out using a model what CO2 levels to expect for various sensitivities. The CO2 proxies confirmed that the CO2 levels were indeed in that range.
OK.
Using the CO2 levels (and best approximations of other greenhouse gases), combined with paleogeographic reconstructions, and progressively lower TSI (as you go back in time according to solar formation models unrelated to AGW) we can reconstruct the paleoclimate of the whole of the Phanerozoic (over 500 million years) that largely agrees with geological evidence. That geological evidence includes fossil evidence, isotope evidence, rock types (such as red beds and evaporites indicating hot dry deserts).
What alternative model explains all that?
You don’t really have an argument. Your position of “other alternatives might be better” isn’t a position, it’s a lack of position.
“BTW, the quote that shows your position unfortunately comes off with a tone quite different than one would expect from someone willing to admit their might be alternatives. Poor communication can only confuse…”
What tone? That I stated what is known? If we know things, then the best hypothesis should include those things.
Your problem is that you are imagining a tone, rather than simply reading the text. Try not applying a tone…
Not “know” but “KNOW”…your back on your old kicks again, shifting the burden, demanding a hypothesis from me…whatever, I really don’t care.
I am always suspicious when I see local effects like the movement of the ice line being examined with a model that treats the Earth’s surface temperature as one-dimensional and in equilibrium. I can’t say I know that it’s wrong, but it doesn’t inspire confidence.
Can I ask, what about water vapour feedback? You may have already lumped it into one of your other variables, but it would be nice to see an analysis that breaks it out separately. We are told that H2O is the principal greenhouse gas, that it accounts for between 60% and 95% of the greenhouse effect, depending on who you listen to, and that by tripling the effects of CO2, its sensitivity to temperature is at least twice that of CO2’s. So where is it? Why isn’t it mentioned?
H2O feedback will of course kick in immediately, and amplify the effects of albedo changes, just as it does for CO2 in the AGW model. If H2O triples the effects of CO2, why would it not triple the effect of albedo change? And if a third of the glacial-interglacial temperature difference is CO2, then is not the rest of it going to be H2O? Or if it isn’t, then isn’t only a proportion of that one-third difference down to CO2?
“We also know with reasonable confidence from atmospheric radiation transfer theory and the characteristics of the infra-red absorption spectrum of CO2 that atmospheric CO2 acts to increase the surface temperature of the planet compared to a planet with no atmosphere.”
This always gets my goat, and I can’t resist arguing every time I see it trotted out again. The greenhouse effect on Earth is not primarily a radiative effect, the warming of the surface compared to a planet with no atmosphere is not directly due to infra-red absorption. I’m not being a crank about this, the mechanism was explained in Soden and Held 2000 and (IIRC) cited by the IPCC.
The greenhouse effect occurs in the troposphere in which heat transfer is regulated by convection, not radiation. The temperature changes with altitude because of air pressure, as indicated by the adiabatic lapse rate (an effect of convection). The average altitude of emission to space settles at the temperature of a planet without atmosphere, and then the air below it down to the surface is at a higher temperature because of the pressure difference. (And incidentally, the air above it is colder than a planet without atmosphere, also because of the greenhouse effect. Explain that with your trapped sunbeams. Ha!) It is not warmer because the IR is in any way “trapped” or “absorbed” and thereby prevented from escaping – it is re-emitted just as fast, and only a fraction of a second’s worth of heat could be retained in this way. (Think about how long it takes sunlight to diffuse through thick cloud – if there’s a total eclipse on a cloudy day, say.) The effect of increasing GHG concentrations on the greenhouse effect is to raise the average altitude from which air emits to space, increasing the thickness of atmosphere and hence pressure difference down to the surface.
It always annoys me, when Al Gore does that picture of happy sunbeams being mugged by nasty CO2 molecules as they try to escape. People have finally figured out that actual greenhouses don’t work that way, now we have to wait for them to discover that the greenhouse effect doesn’t either.
The only one that winds me up worse is the “runaway greenhouse effect” on Venus. There is no runaway greenhouse effect. It is simply that Venus has 92 times more atmosphere. Because of the high altitude opaque clouds its average altitude of emission to space is about 60 km up, and an adiabatic lapse rate of 8K/km does the rest. If you hover at an altitude where the pressure is one Earth atmosphere, the temperature is fairly Earth-like too.
Sorry to rant on so. But I have an ambition – a dream even – that at least all the sceptics should know how the greenhouse effect supposedly works.
It’ll never happen – not even the sceptics listen – but I can’t resist trying.
Peace.
The CO2-feedback hypothesis is implausible, compared to the simpler hypothesis that CO2 is in lagged temperature-dependent equilibrium (cf. http://docs.google.com/fileview?id=0B39QlQ1NSWRENmMxYWQwZGMtNzljNS00NGFiLWFlMTctNTEyNWU3ODhjNTk0&hl=en).
Payne’s complicated analysis looks only at a large-amplitude rise in temperature, where the phase-effect of feedback might pass with a relatively modest blurring of the data. The implausibility becomes indisputable during large-amplitude decreases, such as between 125,000 BC and 105,000 BC.
The simpler hypothesis of equilibrium fits all the data better.
I have a question:
People often talk about what might have cause the positive/negative feedback loops (depending on your bias). What caused the feedback is currently a guess, but we surely know there must be a (strong) temperature negative feedback, because temperature and CO2 have been nearly as high as today and this (according to the Vostok ice cores) caused temperature and CO2 to subsequently drop rapidly back down to ice age levels.
Why do people ignore this obvious negative feeback loop?
If high temperature and high CO2 concentration caused higher temperature and CO2 concentration (positive feedback), wouldn’t the world just keep getting hotter and end up something like Venus?
So surely there MUST be a negative feedback loop that is stonger than the postive feedback?
Just an observation related to the argument that “The onus is on he who contends the alternative is wrong to eliminate it.”
An alternative(s) must first be described in sufficient fso that it can can be tested or evaluated. Failing to define an alternative(s) provides no means to test or evaluate it. In that case it isn’t possible for “one who contends the alternative is wrong” to eliminate it.
Therefore, the onus is on the one suggesting an alternative (exists) to describe it before one can show reason why it is is correct or incorrect.
To simply assert that some other alternative(s) must exist (or that it does exist but that the alternative thus asserted isn’t known) is no different than saying a god exists and that the alternative is that a god doesn’t exist. In other words, you can’t objectively argue with a position or assertion that cannot be tested or evaluated.
It requires no education (or advanced level of intelligence) to assert an alternative exists in order to attempt to refute a hypothesis that has not [yet] been disproven. My 2 year old grand-daughter does that every day.
Sorry Longtooth, I don’t understand what you are getting at. Was your comment directed at me?
It is plainly obvious from the ice cores that, many times in the earth’s history, CO2 and temperature have increased and decreased. I have read that this is not due to orbital precession, or solar activity, but due to changes in the earth’s atmosphere/oceans.
If this is true then there is definitely not a positive feedback loop, becuase otherwise the increases in CO2/temperature would cause an increase in CO2/temperature which would quickly render the world unlivable.
The world is fine now and we have had high levels of CO2/temperature before, so there must be negative feedback in the earth’s atmospheric/ocean systems.
You do NOT need a model to see this.
I believe all climate-related mathematical prediction and current models are totally useless, because the earth’s climate system, which includes surface/atmospheric absorbtion/reflection, shallow/ocean water, evapouration/transpiration, river/glacier movement, cloud cover, groundwater, mountains, the jet stream, plant/plankton growth, ocean currents (constantly changing), ice caps, precipitation, air pressure, to name but a few variables, is just so complex (probably a totally chaotic system) that predicting the state of the earth in the future is currently impossible. I have friends who work at the UK met office, which has one of the world’s best climate models, and they don’t even include the full complexity of the ocean currents…. let alone evapouration!
So I attempt to approach the problem with a more qualataive observation based analysis. But if the qualative observation does contradict the accepted opinion then the “onus” is on the accepted opinion to explain why the observation has not been observed correctly.
I would say it is not possible to argue any alternative objectively, qualative or quantative. Especially when talking about something as complex as the climate. Mathematics/models are objective, but when fitting them to a system you lose the objectivity, especially when the system is so complex.
No climate prediction is testable in our lifetime. The climate is more complex than say, economics, and as such different quantative analysises (models) will give different answers (most likely depending on the users bias), and the time scale is thousands of years, which renders testing in our lifetime invalid.
Perhaps would be better to look at the data more qualatively, as generalisations are possible, whereas models/prediction are currently not.
And actually, logic states, that if one single avenue of the hypothesis is shown to be untrue, the entire hypothesis is invalidated. So if a general argument can be shown to be true, and it invalidates the hypothesis, you can say the hypothesis is false.
So, perhaps, the argument that, many times in the earth’s history the CO2 conc/temperature levels have been high and they have returned to ice age levels, shows that there must be something that “brings it back”. This must invalidate the argument that, (in the past) at high CO2 conc/temp levels there is positive feedback “the runaway greenhouse effect”.
The problem is that the scientists try to make complex predictions from their anaysis of the models, which are just to primitive to be useful.
I believe predicting the stock market is much much easier than predicting the climate, and we can’t even do that, so I really think that we should put less belief in our fatally flawed models.
Re: Stevo (Jun 23 16:46),
Sorry I missed this earlier, but in case anyone is still looking:
More than half the heat transfer in the troposphere is carried by convection, but there would be far less convection if it weren’t for radiation. The upper part of the troposphere loses heat by radiation to space faster than it gains heat by absorption of radiation from the surface. The resulting loss of energy would cause the lapse rate to exceed the adiabatic rate and that is what drives convection. In a transparent atmosphere, there would be much less convection and the altitude of emission would always be at the surface.
Venus did not always have an atmosphere of mostly CO2 with a surface pressure of 92 bar. The runaway greenhouse effect describes the process of how Venus got to be the way it is now. Move the Earth to the same orbital distance as Venus and after some (hundreds of?) millions of years, Earth would look just like Venus as first the oceans boiled away, all organic carbon burned to CO2 and finally all the carbonate was cooked out of the rocks. Water would disappear from the atmosphere as UV absorption splits the water into hydrogen and hydroxyl radicals and at the higher temperature, the hydrogen gradually escapes into space. That process would be slower for the Earth due to the higher gravitational field.